1. Field of the Invention
This invention relates to a multi-speed powershift transmission and more particularly, to a multi-speed powershift transmission for use in an agricultural or industrial type tractor.
1. Description of the Prior Art
History has shown that vehicles of the agricultural and/or industrial type require a wide range of closely spaced speed increments in order to satisfy a variety of working conditions. Such vehicles normally utilize governed engines which provide a relatively constant engine speed but which necessitate numerous gear shifting in order to get the different gear ratios and the correct ground speed. This upshifting and downshifting presents a problem in that the operator must shift without an appreciable disconnection between the driving torque and the load. For example, in plowing with a tractor, a temporary increase in load can be overcome by down-shifting from say seventh to sixth, but if the shift interval is too long, the tractor will lose momentum and a further downshift is required.
The shifting interval problem has been primarily corrected by the use of a powershift transmission which enables an operator to shift gears under full power without clutching. Such transmissions are described in U.S. Pat. No. 3,274,858 issued in 1966 to Meyer et al and U.S. Pat. No. 3,298,252 issued in 1967 to Harris et al. However, most powershift transmissions provide only a limited number of speeds. Therefore, there is a need to provide a transmission with a wide range of closely spaced speed increments which an operator needs for use in various tillage and planting operations. Furthermore, some powershift transmissions cannot provide a good speed selection in all of the needed speed ranges, such as several slow speeds, a range of closer field working speeds and several higher speeds applicable to transport conditions. Now, a multi-speed powershift transmission has been invented which will overcome the deficiencies of the prior art.
The general object of this invention is to provide a multispeed powershift transmission which offers a greater selection of desirable working speeds. A more specific object of this invention is to provide a multi-speed powershift transmission for use in an agricultural or industrial type tractor.
Another object of this invention is to provide a greater number of closely spaced speeds so an operator can utilize the most advantageous speed to optimize productivity.
A further object of this invention is to provide more closely spaced gear speeds within the field working range.
Still further, an object of this invention is to provide a lower gear speed than is normally found in conventional 8-speed powershift transmissions.
Other objects and advantages of this invention will become apparent to one skilled in the art based upon the ensuing description.